Safety arrangement for xerographic fusing apparatus



G. E. SIEMER 3,485,486

SAFETY ARRANGEMENT FOR XEROGRAPHIC FUSING APPARATUS Dec. 23, 1969 5Sheets-Sheet 1 Filed April 18, 1968 INVENTOR GLENN E. SIEMER BY PMATTORNEY.

G. E. SIEMER Dec. 23, 1969 SAFETY ARRANGEMENT FOR XEROGRAPHIC FUSINGAPPARATUS Filed April 18, 1968 5 Sheets-Sheet 2x Dec. 23, 1969 e. E.SIEMER SAFETY ARRANGEMENT FOR XEROGRAPHIC FUSING APPARATUS Filed April18. 1968 5 Sheets-Sheet 5 FIG. 4

POWER SOURCE SINGLE REVOLUTION CLUTCH LATCH OPERATING SOLENOID G. E.SIEMER Dec. 23, 1969 SAFETY ARRANGEMENT FOR XEROGRAPHIC FUSING APPARATUS5 Sheets-Sheet 4 Filed April 18, 1968 G. E. SIEMER Dec. 23, 1969 SAF'ETYARRANGEMENT FOR XEROGRAPHIC FUSING APPARATUS 5 Sheets-Sheet Filed April18, 1968 United States Patent 3,485,486 SAFETY ARRANGEMENT FORXEROGRAPHIC FUSING APPARATUS Glenn E. Siemer, Lexington, Ky., assignorto International Business Machines Corporation, Armonk, N.Y., acorporation of New York Filed Apr. 18, 1968, Ser. No. 722,284 Int. Cl.F27d 11/00, 21/00; F27b 9/06 US. Cl. 263-6 19 Claims ABSTRACT OF THEDISCLOSURE A safety arrangement for apparatus employed to fuse fixablemarking material to a supporting surface, such as a copy sheet, in axerographic copying machine is disclosed. This arrangement preventscharring of a c py sheet or a fire from occurring when the copy sheetbecomes stopped or jammed in the fusing apparatus. The fusing apparatuscomprises a heating unit which is mounted in heat exchange relation withand for movement along the path of travel of the m ving copy sheet. Theheating unit moves from an initial to a final position in the samedirection as and with the moving co y sheet. Under fault conditions, theheating unit is moved to a safety position out of heat exchange relationwith the copy sheet so that the possibility of fire due to Overheatingor charring of a copy sheet in the fusing apparatus is completelyeliminated.

The present invention relates generally to the heating and copying arts.More particularly, the inventi n is directed to providing a safetyarrangement for apparatus used to fuse fixable marking material to asupporting surface in a xerographic or similar copying machine.

The xerographic copying process is well known in the art and employs aphotosensitive element comprising a layer of photoconductive materialsupported on a conductive backing substrate. The process normallyincludes the steps of depositing a uniform electrical charge on thesurface of the photosensitive element while maintaining the element inthe dark, exposing the charged element to a light image of the originalbeing copied, and then developing the latent electrostatic image withfiXable marking material or toner. If the photosensitive element is tobe reused, the toner image is transferred to a sheet of plain paperdefining a copy sheet, usually with the assistance of an externalelectrical field and/or pressure. The fusing apparatus heats and fixesthe toner image on the copy sheet. The finished copy is then transportedto an output hopper where it is accessible to the operator.

The fusing apparatus usually comprises a heating unit which generatessufficient heat to melt or fuse the toner on the copy sheet. The amountof heat which the heating unit must produce to cause fusing of the toneris largely a function of the time available to heat the toner. This inturn is dependent on the relative speed of movement between the heatingunit and the copy sheet. The copy sheet becomes rapidly overheated if itis st pped or becomes jammed within the fusing apparatus. Further, whena jam occurs, portions of the copy sheet may be close to or in actualcontact with the heating lamp or other hot elements of the fusingapparatus. A serious safety hazard is presented since a fire can bestarted in the fuser apparatus under these conditions.

The problems of charring of the copy sheets and fires in the fusingaparatus of xerographic copying machines have been previously recognizedin the art and various solutions have been proposed. For example, it isknown to employ shutters between the heating unit and the copy sheet.The shutters automatically close to protect the copy 3,485,486 PatentedDec. 23, 1969 sheet under fault conditions. Further, it has beensuggested to automatically pivot the heating units or move the copysheet supporting means to in operative positions when a fault conditionoccurs. While these arrangements are satisfactory under many operatingcondition, they require relatively expensive apparatus which and haveincreased the overall costs of xerographic copying machines.

It is the primary or ultimate object of the invention to provide animproved safety arrangement for xerographic fusing apparatus. The fusingapparatus comprises a heating unit which is moved from an initial to afinal position along the path of travel of the copy sheet when a copysheet is transported thr ugh the fusing apparatus. This arrangementsubstantially increases the time interval during which the copy sheet isin heat exchange relation with the heating unit. Means are provided tomove the heating unit to a safety position under various faultconditions. When in the safety position, the heating unit is out of heatexchange relation with the copy sheet and the possibility of a firestarting in the fusing apparatus is completely eliminated.

Another object of the invention is the provision of a safety arrangementfor xerographic fusing apparatus which incorporates means for m ving theheating unit to a safety position whenever a fault condition isdetested. The drive for moving the heating unit between initial andfinal position during normal fusing operations comprises a cam and camfollower mechanism. Under fault conditions the cam follower mechanism iscollapsed from operative cam following relation with the cam andautomatically moved to a predetermined safety stop position. The heatingunit immediately moves to its safety position as the cam followermechanism goes to its retracted safety stop position.

A further object of the invention is to provide a safety arrangement forxerographic fusing apparatus which includes structure for aut maticallyreturning the heating unit from the safety to an operative heat fusingposition when it is desired to resume normal heat fusing operations. Theoperator is not required to take any action other than to remedy orclear the fault condition which caused the heating unit to move to itssafety position. The cam follower mechanism is automatically returned tooperative cam following relation with the drive cam and the heating unitmoves back to an operative fusing position when the drive for the fusingapparatus is reenergized.

A still further object of the invention is to provide a safetyarrangement for xerographic fusing apparatus having the characteristicsset forth above which is extremely simple in construction and operation.The safety arrangement involves the addition of only a minor number ofinexpensive parts to the basic fusing apparatus.

The foregoing and other objects and advantages of the invention will beapparent from the following more particular description of a preferredembodiment of the in vention as illustrated in the accompanyingdrawings.

In the drawings:

FIGURE 1 is a schematic side view of a xerographic copying machineemploying fusing apparatus having a traversing heating unit embodyingthe safety arrangement of this invention.

FIGURE 2 is a side sectional view from the opposite side of thexerographic copying machine in relation to the view of FIGURE 1 showingin more detail the construction of the fusing apparatus;

FIGURE 3 is an enlarged and fragmentary side sectional view of thetraversing heating unit showing particularly the quartz heating lamp andthe reflector therefor;

FIGURE 4 is a plan view of the fusing apparatus which particularlyillustrates the cam controlled drive mechanism for moving the traversingheating unit between safety, initial and final positions;

FIGURE 5 is a plan view of the vacuum plenum;

FIGURE 6 is a fragmentary end sectional view taken generally along thesection line 66 of FIGURE 2;

FIGURE 7 is a fragmentary plan view similar to the view of FIGURE 3showing the positions of the various parts of the cam follower mechanismwhen the heatin unit is in its final position;

FIGURE 8 is a fragmentary plan view indicating the positions of theparts of the cam follower mechanism when the heating unit is located inthe protected or safety position; and

FIGURE 9 is a fragmentary plan view showing the positions of thedifferent parts of the cam follower mechanism when the heating unit ismoved from the protected or safety position to the initial positionpreparatory to resuming normal fusing operations.

XEROGRAPHIC COPYING MACHINE Referring now to the drawings, and initiallyto FIG- URE 1 thereof, there is shown a schematic representation of axerographic copying machine embodying the safety arrangement for thefusing apparatus of the present invention. The electrophotographicmember of the copying machine comprises a drum 10 which is mounted forrotation in the direction indicated by arrow 11. Disposed on the outerperiphery of the drum is a thin layer of photosensitive material 12which is supported on a conductive substrate. The photosensitivematerial is preferably an organic photoconductor comprising a one-to-onemolar ratio of polymerized vinylcarbazole and 2, 4, 7-trinitro-9-fluorenone which is disclosed and claimed in an application ofMeredith D. Shattuck and U10 Vahtra entitled Organic PhotoconductiveCompositions and Their Use in Electrophotographic Processes, Ser. No.556,982, filed June 13, 1966, and assigned to the assignee of thisinvention. The photoconductor is coated on a flexible conductive backingmaterial and stored on reels within the interior of the drum to permitreplacement or changing of the operative photoconductor surface withoutremoving the drum from the machine as is disclosed and claimed in anapplication of Clifford E. Herrick, Jr. entitled ElectrophotographicProcess, Ser. No. 649,162, filed June 27, 1967 and assigned to theassignee of the present invention. While the disclosed photoconductorand drum construction are preferred, the present invention is concernedwith fusing apparatus and is not dependent on the use of any particularelectrophotographic member.

Disposed about the periphery of the drum 10 are a number of processingstations which carry out the conventional steps of the xerographiccopying process. An initial charging station is provided by a coronaunit 13 which deposits a uniform charge on the surface of thephotosensitive material while the same is maintained in the dark. Thenext station is exposure station 14 where a line image of the originaldocument is projected onto the uniformly charged surface of thephotosensitive material 12 as the drum rotates. A document 15 to becopied is supported face down on a movable and transparent copy bed 16which moves back and forth past a scanning slit as indicated by thearrow 17. The document 15 passing the scanning slit is illuminated bylights 18 and a line image of light and shadow is projected bystationary lens 19 onto the photosensitive material 12 carried by thedrum.

The next station in the direction of rotation of the drum 10 is acascade developer unit 20 where a two component developer composition iscaused to move across the surface of the drum. The developer compositioncomprises heat fixable marking particles or toner which is attracted toand deposited on the surface of the photosensitive member in accordancewith the latent electrostatic image 4 corresponding to the original. Theresult of the cascade development operation is the formation of a tonerimage on the surface of the drum. It is now necessary to transfer thetoner image to a copy sheet and this is accomplished at the tonertransfer station 22.

The plain copy paper is stored within the copying machine in roll formas indicated by roll 24 and is fed along a path of travel 25 in thedirection indicated by the arrows leading past knives 26, toner imagetransfer station 22, fusing apparatus generally indicated by referencenumeral 27 and then to an output copy hopper 28. The copy paper is cutto the length selected by the operator and the cut copy sheet moves intocontact with the drum. A transfer corona unit 29 assists in the transferof the toner image to the copy sheet. The copy sheet is then separatedfrom the drum, the toner image fused by heat and the final copytransported to the output hopper 28.

Not all of the toner image is transferred to the copy sheet and it isnecessary to remove the residual toner from the surface of the drum.This is accomplished by employing a preclean corona unit 30 whose coronadischarge tends to loosen the remaining toner particles and a cleaningbrush 31 which is rotated at high speed in the direction indicated byarrow 32. The toner particles which are brushed from the surface of thephotosensitive material are drawn by vacuum into a filter bag mountedwithin a housing 33.

The above description of a representative xerographic copying machine isnot intended to limit in any manner the teachings or claims of thisinvention. The principles of the safety arrangement disclosed in thisspecification can be employed with any of a wide variety of copyingmachines or systems.

FUSING APPARATUS The fusing apparatus 27, as shown in FIGURES 1 and 2 ofthe drawings, is located along the upwardly inclined path of travel 25of the copy sheets between the toner image transfer station 22 and theoutput hopper 28. It should be understood at the outset that the claimsof the present application are limited to the safety arrangement for thefuser apparatus. The fuser apparatus itself is claimed in the co-pendingapplication of James V. Cely and Robert T. Ritchie, Ser. No. 697,734,filed Jan. 15, 1968 entitled Xerographic Fusing Apparatus and which isassigned to the assignee of this invention.

The fusing apparatus comprises an elongated and stationary vacuum plenum35 located below the path of travel which provides a means forsupporting and transporting copy sheets through the fusing apparatus anda heating assembly 36. The heating assembly 36 is positioned above thepath of travel 25 of the copy sheets in opposed overlying relation withrespect to the vacuum plenum 35. The operative element of the heatingassembly 36 is a heating unit 37 provided by a quartz heating lamp 38and a reflector 39. The lamp 38 and the reflector 39 are elongated andextend transversely across the path of travel 25 of the copy sheets. Theinner surface 40 of the reflector 39 is generally elliptical and highlyspecular. The heating lamp 38 is connected to a source of electricalenergy which is preferably a standard and conventional electrical outletfound in any room since special wiring for supplying the necessaryelectrical power is not required. The heating lamp 38 and the reflector39 cooperate to produce a transversely extending and relatively narrowband of infrared radiation on the surface of a copy sheet which, becauseof the unique mounting and movement of these members, is suflicient tofuse the toner image to the copy sheet.

The heating lamp 38 is preferably clip or spring mounted at its endswithin the reflector 39 to permit easy removal and replacement. Thereflector is formed from good heat conducting material and has a pair ofupturned and vertically extending end walls 41 which nestingly receiveand are joined to the depending legs of an elongated and transverselyextending channel shaped carriage member 42. Wires 43 for supplyingelectrical power to the heating lamp 38 run the length of the heatingunit 37 in the space between the reflector 39 and the carriage member42.

Connected to each end of the reflector 39 and the carriage member 42 isa mounting bracket 44 which carries a roller 45. The rollers 45 at theopposite end of the heating unit 37 engage and ride on the outer upperedges of a large and generally U-shaped heating assembly housing member46. The upper surface of the carriage member 42 as provided with a pairof buttons 47 at each end thereof.,The buttons are formed from amaterial having a low coefficient of friction and engage the outer loweredges of the housing member 46 in opposed relation to the rollers 45.

The heating assembly housing member 46 generally overlies the vacuumplenum 35 and its outer edges define a pair of transversely spaced andlongitudinally extending side rails 48 which are engaged on the top andbottom by the rollers 45 and the pairs of buttons 47 at opposite ends ofthe transversely extending heating unit 37. The arrangement is such thatthe heating unit 37 comprising the heating lamp 38 and the reflector 39is mounted in a highly simplified but rugged manner for traversingmovement back and forth along the path of travel 25 of the copy sheets.In operation, the heating unit 37 moves from an initial position 50 to afinal position 50 indicated by the broken line representation of theheating unit as a copy sheet moves along the path of travel 25 throughthe fusing apparatus. After the fusing operation, the heating unit 37 isreturned to its initial position.

Attached to the forward end wall of the heating assembly housing member46 is a generally T-shaped heat shield 150. The heat shield is formedfrom highly heat absorbing material and has a relatively thick crosssection. The shield 150 provides an open ended heating unit receivingpocket 151 at the forward end of the fusing apparatus. Under faultconditions the heating unit 37 is automatically moved to a safetyposition 50" within the pocket. The heat shield 1'50 serves not only asa heat isolating barrier between the copy sheet and the hot elements ofthe heating unit, but also as a means for quickly absorbing radiatedheat from the hot elements of the heating unit to cool the latter belowthe temperature where they might cause a fire in the fusing apparatus.The forward end of the shield 150 is turned upwardly to provide atransversely extending guide 152 which assists in guiding the leadingend of a copy sheet into the fusing apparatus. The rear end 153 of theheat shield 150 is curved upwardly to prevent accidental curling of theend of a copy sheet within the pocket 151 under fault conditions.However, sufficient clearance is maintained between the heat shield 150and the top wall of the heating assembly housing member 46 to permit theheating unit 37 to freely move to its safety position 50'. It isimportant to note that during normal fusing operations the heating unitdoes not enter the pocket 151 and the heat shield 150 is maintained in arelatively cool and unheated state so that it can absorb the heat fromthe hot elements of the heating unit. The heating unit 37 is moved toits safety position 50" anytime a fault condition is detected and fromany point along its normal path of travel. The drive means for movingthe heating unit between initial, final and safety positions will bedescribed in detail in a following portion of the specification.

The heat required to fuse the toner image to a copy sheet can beexpressed in terms of the following generalized time dependent equation:

A T mCp E where:

AQ=heat required to fuse the toner m=mass of the toner Cp=constantpressure specific heat of the toner AT=temperature rise of the tonerrequired to fuse the same At=time required to fuse the toner to the copysheet The use of a traversing heating unit 37 permits the effective time(At) during which heating and fusing of the toner occurs to beappreciably extended so that the overall efiiciency of the fusingoperation is improved. In general, less energy is required using thisfusing apparatus than is necessary in prior art apparatus of the samegeneral type where the heating unit is stationary during the fusingoperation.

For example, in a constructed embodiment of the invention, the copysheets move through the fusing apparatus at a speed of four inches persecond while the traversing heating unit moves with a copy sheet at aspeed of one and two-tenths inches per second. The result of moving theheating unit in this manner is that the copy sheet moves two andeight-tenths inches per second relative to the heating unit. Theapproximately thirty percent reduction in the relative speed of travelbetween the heating unit and the copy sheet compared to similarapparatus employing a stationary heating unit substantially increasesthe time available to accomplish fusing of the fixable marking material.The heating lamp employed in this constructed embodiment was of thequartz infrared halogen atmosphere type available from Sylvania ElectricProducts, Inc. and was rated for operation at 1350 Watts, volts. Thepower requirements were supplied from a conventional 115 volt-15 ampereelectrical wall outlet employing a standard wiring and the toner imageswere satisfactorily fused to the copy sheets under all conditions.

A very important aspect of the xerographic fusing apparatus is that nowarm-up time is required to properly fuse the toner. The fusing unit isavailable for immediate use whereby the first copy is delivered to theoutput hopper as quickly as the other steps of the xerographic processcan be completed and the sheet of copy paper moved through the machine.The time required to produce the first copy is not dependent on thefusing area reaching a predetermined temperature which in turn isdependent on how recently the xerographic copying machine has been used.Further, in the constructed embodiment of the invention, it was notnecessary to partially energize the heating lamp during standbyconditions. This reduces the overall power requirements for thexerographic copying machine and is particularly important in aninstallation where the machine is used rather infrequently and partialenergization of the heating lamp is inefficient.

The drive mechanism for moving heating unit 37 between initial and finalposition 50 and 50 and, under fault conditions, quickly moving theheating unit to the safety position 50 is best shown in FIGURES 4 and7-9 of the drawings since its primary components are mounted on the topsurface of the heating assembly housing member 46. A verticallyextending shaft 52 is rotatably supported by a collar in the center ofthe housing member 46. Attached to the shaft 52 are a relatively largecam 54 having a profiled camming surface 55 and an upwardly facing bevelgear 56. Meshing with the teeth of the bevel gear 56 are the teeth ofanother and normally related bevel gear 57 which is pinned to thetransversely extending drive shaft 58. The bevel gears 56 and 57 providea right angle drive connection between the drive shaft 58 and thevertical mounting shaft 52. The drive shaft 58 is supported for rotationin the upstanding walls of a pair of brackets 59 attached to oppositesides of the heating assembly housing member 46 and is connected byclutch 60 to a source of mechanical power 61. The clutch 60 ispreferably of the single revolution type and is actuated by timingcircuits, not shown. The arrangement is such that as the leading edge ofa copy enters the fusing apparatus, the clutch 60 is energized and thecam 54 rotates clockwise through a complete revolution. During this timethe heating unit 37 moves from its initial position 50 to its finalposition 50 as the copy sheet moves through the fusing apparatus andthen the heating unit returns very quickly to its initial position 50.The activation of the single revolution clutch 60 is, of course,synchronized with the cutting and feeding of the copy sheets, therotation of the xerographic drum and the movement of the transparentcopy bed 16.

A cam follower mechanism is generally designated by the referencenumeral 120 and comprises a cam follower roll 65 which engages theperiphery or camming surface 55 of the cam 54. The cam follower roll 65is rotatably mounted on the forward end of a carrier member 121. Thecarrier member 121 is pivoted on a vertically extending pin 68 andoverlies one arm 66 of bell crank 67 which is also mounted for pivotalmovement about the pin 68. A latch member 122 overlies the carriermember 121 and is pivoted to the latter by the pivot pin 123. The latchmember 122 has a stepped latch surface 124 at its outer end which isadapted to engage an upturned tab 125 extending from arm 66 of the bellcrank 67. The latch member is provided with a second stepped latchsurface 126 Whose function will be hereinafter more fully explained. Aspring 127 interconnects the lower end of the latch member 122 withspring mounting post 128 on the other arm of the bellcrank 67 and biasesthe latch member clockwise. Another spring 129 extends between themounting post 128 and the lower end of the carrier member 120.

The lower end of the latch member 122 is connected by a flexible driveconnection schematically represented by reference numeral 130 to asolenoid 131. This solenoid 131 is energized to rotate latch member 122counterclockwise against the action of spring 127 by suitable electricalcontrol circuits, not shown, whenever a fault condition is detected. Anydesired fault condition or conditions can be employed to actuate thesolenoid, such as the energization of the emergency off control circuitsfor the xerographic copying machine and/ or the absence of a copy sheetat the output of the fusing apparatus within a predetermined timeinterval of its introduction into the fuser apparatus as indicated by aplurality of copy sheet presence detector switches located along thepath of travel of the copy sheets.

When the cam follower mechanism is latched in its operative position asshown in FIGURE 4 of the drawings, the cam follower roll 65 is biasedinto following engagement with the camming surface 55 of the cam 54 by astrong spring 69 which extends from the spring mounting post 128 andshorter arm of the bellcrank 67 to a stationary anchor pin 70 on theheating assembly housing member 46. Pivoted on pin 133 and locatedintermediate the ends of the arm 66 of bellcrank 67 is an overcenterresetting member 134. This member has an enlarged opening 133 thereinwhose edges cooperate with a stop pin 136 carried on the bellcrank armto limit the pivotal movements thereof. The resetting member 134 isbiased in either of its stable overcenter positions by a hairpin typespring 138 that extends from an upstanding tab 139 on this member to aspring mounting post 140 adjacent the end of the bellcrank arm 66. Theresetting member 134 has a pair of surfaces 141 and 142 on oppositesides thereof which are adapted at certain times to engage and cooperatewith a reset pin 143 and a stop pin 144, respectively, mounted on theheating assembly housing member 46. The resetting member 134 also has anintegral projecting arm 146 which, under certain operating conditions,engages a stationary stop pin 147 mounted on the heating assemblyhousing member 46 to hold the bellcrank in an intermediate position. Theuse of the resetting member 134 and the various reset and stop pinswhich cause automatic relatching of the cam follower mechanism 120 whennormal fusing operations are resumed and the heating unit is returnedfrom the safety to an operative fusing position will be hereinafter morefully explained.

Attached to the outer end of the arm 66 of the bellcrank 67 is a link 71which carries at its ends a pair of pulleys 72 and 73. Entrained aboutthese pulleys are the opposite ends of a non-extensible and fixed lengthcord 75. As the pulleys 72 and 73 move back and forth in an arc definedby the length of the bellcrank arm 66 and the shape of the cammingsurface 55 when the cam follower mechanism is latched in operativerelation, the cord 75 is pulled back and forth along a defined path.

Mounted from the brackets 59 attached to opposite sides of the heatingassembly housing member 46 are pulleys 78-81. These pulleys are locatedat the corners of the heating assembly housing member and, incombination with additional pulleys 82 and 83 on the housing member 46and the movable pulleys 72 and 73 carried by link 71, define the path oftravel for the cord 75. The cord 75 extends from a stationary mountingpoint 84 for one end thereof, around movable pulley 72, then aboutstationary pulleys 83, 79, 78, 82, 81 and in the order indicated, andabout movable pulley 73 to one end of a relatively strong spring 85. Theother end of the spring 85 is anchored at 86 to the heating assemblyhousing member 46. The spring 85 is provided to take up any slack in thecord 75 and maintain it tight in its path. The path of the cord 75 issuch that the portions 87 and 88 thereof extending between thestationary pulleys 80-81 and 78-79 located on opposite sides of theheating assembly housing member will move in the same direction and bythe same distance in response to movements of the movable pulleys 72 and73 under control of the rotating cam 54 and cam follower roll 65. Themounting brackets 44 located at the opposite ends of the transverselyextending heating unit 37 are attached to the cord 75 at the pointsindicated by the marks 89. The drive mechanism moves the heating unit 37back and forth between its initial and final positions 50 and 50' overthe path of travel 25 of the copy sheets in accordance with the profileof camming surface 55 of cam 54 to substantially lengthen the time thata copy sheet remains in operative relation with the heating unit.

The vacuum plenum 3 is shown in detail in FIGURES 2, 5 and 6 of thedrawings and comprises a generally elongated and fiat housing 90 formedfrom sheet metal or similar material and having a pair of enlargedpockets 91 and 92 at the ends thereof. Rotatably supported within thepocket 92 is a relatively large diametered drive roll 93. The drive roll93 has a pair of side flanges and a plurality of transversely spacedridges 94 which define guiding means for a plurality of transverselyspaced endless copy sheet carrying belts 95. The belts are preferablyfabricated from heat resistant fabric material having a high coefficient of friction and may be rubber coated or impregnated to betterengage and hold the copy sheets. A power source 96 (see FIGURE 5) isdrivingly connected to and continuously rotates the drive roll 93 whenthe vacuum plenum is latched in its operative position.

Disposed within the housing pocket 91 are a plurality of transverselyaligned belt tensioning rolls 97. One of these rolls is associated witheach of the endless copy sheet carrying belts 95. Each of the tensioningrolls 97 is rotatably supported in its individual slidable carrier 98that is biased by a spring 99 toward the entrance end of the fusingapparatus. Rollers 100 and 101 are journalled in the housing 90 adjacentits ends and further guide the belts along the lower portions of theirpaths of travel. The arrangement is such that the endless belts 95 areproperly guided, tensioned and driven to transport copy sheets throughthe fusing apparatus.

Supported within and adjacent the top surface of the housing 90 of thevacuum plenum and between the drive roll 93 and the tensioning rolls 97are a plurality of longitudinally extending sheet metal plates or slats103. The plates 103 provide the top surface of the vacuum plenum andsupport the endless belts 95 along the upper portions of their paths oftravel. These plates are transversely spaced from each other to definelongitudinally extending openings or slits 104 between the transverselyspaced endless copy sheet carrying belts 95. In addition, a pair ofslots 105 are formed in the outermost pair of plates 103 and underliethe two rows of apertures 106 provided in the outermost of the endlessbelts 95.

The slits 104 between the plates, the spaces between the adjacent edgesof the endless belts, the slots 105 and the rows of apertures 106 definea plurality of longitudinally extending and transversely spaced portsfor applying vacuum pressure to the back of a copy sheet as it istransported through the fusing apparatus. The copy sheet is firmly heldto the driven endless belts without disturbing the toner image on theface of the copy sheet or interfering in any way with the fusingoperation. It is noted that the transverse spacing between the two rowsof apertures 106 in the outermost belts is approximately equal to thewidth of the copy sheets. This has been found particularly effective inpreventing curling of the side edges of the copy sheet due to thermalshock caused by the very rapid evaporation of moisture from the copysheet.

One side of the vacuum plenium housing 90 is formed with an elongatedand vertically tapered vacuum port 108 that is best shown in FIGURE 6 ofthe drawings. The port 108 cooperates with the complementary tapered endof a passageway 109 which extends from the stationary frame ofxerographic copying machine. The passageway 109 is in communication witha vacuum source 110. The various adjacent edges of the vacuum port 108and passageway 109 are overlapped to reduce the loss of vacuum pressure.This arrangement, While being sufiiciently fluid tight to prevent unduelosses in vacuum pressure, permits the vacuum plenum to be pivoted downto an open position without requiring disconnection of vacuum lines orany other special operations on the part of the operator. Also, the useof flexible vacuum lines or conduits which require relative frequentreplacement has been avoided.

The end of the vacuum plenum at the entrance to the fusing apparatus ispivoted to the stationary frame 115 of the xerographic copying machineby a pair of laterally projecting pivot pins 116. The other end of thevacuum plenum 35 carries a pair of transversely extending locking pins117 which cooperate with a pair of spring biased latches 118 that arepivotally mounted from the frame of the Xerographic copying machine.This mounting arrangement for the vacuum plenum is highly advantageoussince the operator need only release the latches 118 and the vacuumplenum is pivoted down to about pivot pins 116 to completely expose theinterior of the fusing apparatus. Any jams of copy sheets within thefuser apparatus can be quickly cleared and routine maintenance, such asperiodic replacement of the quartz heating lamp 38, is greatlyfacilitated. The latches 118 are of the self latching type and aredesigned to automatically engage and latch the locking pins 117 in theposition shown in FIGURE 2 of the drawings when the vacuum plenum ispivoted upwardly to its closed position.

OPERATION Considering now the operation of the xerographic fusingapparatus of this invention, it will be assumed that the heating unit 37is in its initial position and the endless belts 95 are being driven ina direction to advance copy sheets upwardly through the fusing apparatusalong the path of travel 25. As a copy sheet having a toner imagethereon is stripped from the drum, it is transported into the fuserapparatus over a guide 119 located at the entrance end of the vacuumplenum (see FIGURE 2). The guide 152 formed by the forward end of theshield 150 assists in guiding the copy sheet into the fusing apparatus.When the leading edge of the copy sheet enters the fusing apparatus, thesynchronizing timing circuits actuate the single revolution clutch 60 sothat cam 54 is rotated clockwise through a complete revolution. The riseof the cam surface 55 is such that the heating unit 37 advances in thesame direction as the copy sheet at a substantially constant velocity.As previously explained, the velocity of the heating unit 37 is lessthan that of the copy sheet but it is sufficient to substantiallyincrease the time that the heating unit is in operative fusing relationwith the copy sheet. During its movement through the fusing apparatus,the copy sheet is held in a fiat condition by the vacuum pressureapplied to the back of the sheet.

As the trailing edge of the copy sheet with the fused image thereonleaves the fusing apparatus, the heating unit 37 has reached its finalposition 50', and the position of the cam follower mechanism 120 at thistime is shown in FIGURE 7 of the drawings, The cam follower roll 65moves from the highest rise portion to the dwell of the cam 54 and theheating unit returns quickly to its initial position under the action ofspring 69. The length of time required to return the heating unit to itsinitial position is very short so that it is ready to fuse the tonerimage to the next copy sheet when the latter is introduced into thefusing apparatus. The above described fusing operation is repeated in anuninterrupted manner as copy sheets are successively introduced into thefusing apparatus and as long as no fault conditions are detected.

When a fault condition is detected, such as when the operator actuatesthe emergency off control circuits for the xerographic copying machineor a copy sheet has not passed from the fusing apparatus in apredetermined time period after its introduction into the fusingapparatus, the solenoid 131 is immediately energized to rotate the latchmember 122 counterclockwise against the action of spring 127. The effectof the counterclockwise rotation of the latch member 122 is to decoupleand permit relative. pivotal movement between the carrier 121 mountingthe cam follower roll 65 and the bellcrank 67 carrying the pulleys 72and 73 which control the movement of cord 75 in its path of travel. Thecam follower roll 65 remains in contact with the camming surface 55 ofthe cam 54 while the bellcrank is immediately pivoted clockwise to anextreme safety position where arm 66 engages the stop pin 144 mounted onthe top of the heating assembly housing member 46. The positions of theparts of the cam follower mechanism 120 at this time are shown in FIGURE8 of the drawings.

The bellcrank 67 has been effectively disconnected from its drivingrelation with the cam 54 and moved to a safety position which is belowor more clockwise than the extreme clockwise position provided by thelowest or dwell portion of the camming surface 55 during normal fusingoperations. The movement of the pulleys 72 and 73 to the positionsillustrated in FIGURE 8 moves the cord 75 in its path of travel to theextent necessary to move the heating unit 37 to its safety position 50"within the pocket 151 provided by the heat shield 150. This movement ofthe heating unit 37 occurs very quickly due to the action of therelatively strong spring 69. It is noted that the heating unit may bemoved to the safety position 50 in response to detection of a faultcondition at any time during a fusing operation and without reference tothe position of the cam follower roll 65 on the camming surface 55 ofthe cam 54.

The fault condition detection control circuits are operative to cut offenergizing power from the heating lamp 38 simultaneously with theenergization of the latch member actuating solenoid 131. The safetypocket 151 and the heat shield are relatively cool when a faultcondition is detected since the heating unit is not received in thepocket 151 at any time during normal fusing operations. The shield 150-acts as a barrier which prevent a copy sheet within the fusing apparatusfrom being overheated or coming in contact with the hot elements of theheating unit. Further, the radiated heat from the hot elements of theheating unit is absorbed by the relatively cool parts surrounding thepocket 151 to quickly lower the temperatures of these elements. The useof this safety arrangement is effective in preventing fires in thefusing apparatus and damage to the copy sheets.

After the operator has cleared the fault condition, it is necessary toreturn the heating unit 37 to an operative fusing position where it isagain in heat exchange relation with a copy sheet moving along the pathof travel 25. This function is accomplished by the resetting member 134and the reset and stop pins 143, 144 and 147. Under normal operatingconditions of the fusing apparatus, the resetting member 134 is pivotedto its lower stable position (see FIGURE 2) so that its arm 146 clearsthe stop pin 147 as the bellcrank arm pivots back and forth in an arcabout pivot pin 68 under the control of the camming surface 55 of cam54. However, when a fault condition is detected, the bellcrank arm 66quickly moves to a position against stop pin 144. As the bellcrank armapproaches this stop pin, the latter engages surface 142 of theresetting member 134 and moves the same sufiiciently so that overcenterspring 138 forces the resetting member to its other stable position. Thedisposition of the various parts of the cam follower mechanism at thistime is shown in FIGURE 8 of the drawings.

When the drive mechanism is re-energized the cam 54 begins to rotate andeventually the cam follower roll 65 will reach the dwell or lowest pointon the surface of the cam 54. During this movement of the cam followerroll 65 and the carrier 121, the latch member 122, which is pivoted tothe carrier 121 by pivot pin 123, moves clockwise sufiiciently toposition its stepped latch surface 126 behind and in engaging relationwith the tab 125 extending from the bellcrank arm 66.

Continued rotation of the cam 54 causes the entire cam followermechanism 120 to be pivoted counterclockwise about pivot pin 68 with thelatch surface 126 engaging the tab 125. During this movement of the camfollower mechanism, the arm 146 of resetting member 134 rides past thestop pin 147 without switching the position of the resetting member 134and then drops behind the stop pin 147 The positions of the variousparts when the cam follower roll 65 is adjacent the high rise portion ofthe cam 54 is shown in FIGURE 9 of the drawings. At this time theheating unit 37 is located adjacent its initial position 50.

The cam 54 continues to rotate and the cam follower roll 65 moves downthe sharp drop on the camming surface to the dwell point of the cam. Thecarrier member 121 and the latch member 122 pivot clockwise about pivotpin 68, but the arm 66 of bellcrank 67 is held in an intermediateposition and prevented from moving clockwise by the arm 146 of resettingmember 134 which is now positioned behind and engages the stop pin 147.As the cam follower roll 65 reaches the dwell of the cam, the steppedlatch surface 124 of latch member 122 drops behind the tab 125 ofbellcrank arm 67 and the heating unit 37 is located adjacent its initialposition 50. The fusing apparatus is now ready to resume fusingoperations. During the first fusing operation, the surface 141 of theresetting member 134 engages reset pin 143 located on the top of thehousing member 46 to flip the resetting member to its other stableposition. This removes the arm 146 of resetting member 134 from engagingrelation with the stop pin 147. The cam follower mechanism 120 is now inits initial latched condition or state. Subsequent energization of thesolenoid 131 in response to the detection of a fault condition willautomatically result in the heating unit again being moved to its safetyposition 50" in pocket 151 provided by heat shield 150.

It should now be apparent that the objects initially set forth have beenaccomplished and that various changes can be made in the disclosedembodiment without departing from the teachings of the invention. Forexample, the solenoid for actuating the latch member can be arranged sothat the latch member is maintained in its latched state only as long asthe solenoid is energized so that if power is lost for any reason theheating unit is moved to the safety position. Also, if the heating unitmoves too quickly to the safety position when a fault condition isdetected, a damping means can be included either Within the pocket or ontop of the heating assembly housing member to prevent shock damage tothe heating lamp. The heating unit may comprise more than one heatinglamp or other types of heating elements. The fusing apparatus hasapplication in a wide variety of copying systems other than thoseemploying dry toner particles. It may be used to evaporate the solventfrom and/or dry copy sheets in a copying system employing liquiddevelopment techniques and the term fusing as employed in thisspecification and the claims is intended to include and cover the use ofdisclosed method and apparatus for these purposes.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formand details may be made therein without departing from the spirit andscope of the invention.

What is claimed is:

1. Apparatus for fusing an image on a copy sheet in a copying system orthe like comprising:

means to move a copy sheet in one direction along a path of travel;

a fusing unit located in fusing relation with a copy sheet moving alongsaid path of travel; means mounting said fusing unit for movement alongsaid path of travel in said one direction from an initial position to afinal position and for movement to a retracted safety position out offusing relation with a copy sheet moving along said path of travel;

means to move said fusing unit from said initial position to said finalposition when a copy sheet is moving along said path of travel adjacentsaid fusing unit to extend the time the copy sheet is in fusing relationwith said fusing unit;

. means to move said fusing unit to said retracted safety position outof fusing relation with a copy sheet; said fusing unit comprises aheating unit disposed in heat exchange relation with a copy sheet movingalong said path of travel; and

a heat shield at said retracted safety position which is disposedbetween said heating unit and said path of travel when said fusing unitis located in said retracted safety position.

2. Apparatus for fusing an image on a copy sheet in a copying system orthe like comprising:

means to move a copy sheet in one direction along a path of travel;

a fusing unit located in fusing relation with a copy sheet moving alongsaid path of travel; means mounting said fusing unit for movement alongsaid path of travel in said one direction from an initial position to afinal position and for movement to a retracted safety position out offusing relation with a copy sheet moving along said path of travel;

means to move said fusing unit from said initial position to said finalposition when a copy sheet is moving along said path of travel adjacentsaid fusing unit to extend the time the copy sheet is in fusing relationwith said fusing unit; means to move said fusing unit to said retractedsafety position out of fusing relation with a copy sheet;

said means to move said fusing unit comprises means to return saidfusing unit from said final position to said initial position after acopy sheet has move'd from fusing relation with said fusing unit; and

means to move said fusing unit from said retracted safety position to aposition in fusing relation with a copy sheet moving along said path oftravel.

3. Apparatus for fusing an image on a copy sheet in a copying system orthe like comprising:

means to move a copy sheet in one direction along a path of travel;

a fusing unit located in fusing relation with a copy sheet moving alongsaid path of travel;

means mounting said fusing unit for movement along said path of travelin said one direction from an initial position to a final position andfor movement to a retracted safety position out of fusing relation witha copy sheet moving along said path of travel;

means to move said fusing unit from said initial position to said finalposition when a copy sheet is moving along said path of travel adjacentsaid fusing unit to extend the time the copy sheet is in fusing relationwith said fusing unit;

means to move said fusing unit to said retracted safety position out offusing relation with a copy sheet;

said means to move said fusing unit from said initial position to saidfinal position comprises a cam;

cam follower means drivingly interconnecting said cam and said fusingunit;

means to effect relative movement between said cam and said cam followermeans; and

said means to move said fusing unit to said retracted safety positioncomprises means to disengage at least a portion of said cam followermeans from driven relation with said cam.

4. Apparatus according to claim 3 further characterized by:

said cam follower means comprises a cam follower element engaging saidcam;

a plurality of relatively stationarily mounted rotatable pulleys and ateast one rotatable pulley which is mounted for translational movement;

a linkage means rigidly interconnecting said cam follower element andsaid pulley which is mounted for translational movement;

a flexible member extending in a path of travel about said pulleys; and

said fusing unit being connected to said flexible member so that saidfusing unit moves along said path of copy sheet travel upon actuation ofsaid means to effect relative movement between said cam and said camfollower means.

5. Apparatus according to claim 4 further characterized by:

said linkage means comprising a pair of levers;

one of said levers mounting said rotatable pulley which is mounted fortranslational movement;

the other of said levers mounting said cam follower element;

a latch member normally maintaining said pair of levers in rigid coupledrelation with respect to each other;

biasing means connected to said one of said levers for maintaining saidcam follower element in engagement with said cam; and

means to actuate said latch member to cause movement of said one of saidlevers relative to said other of said levers, said cam follower elementand said cam to move said fusing unit to said retracted safety position.

6. Apparatus for fusing an image on a copy sheet in a copying system orthe like comprising:

means to move a copy sheet in one direction along a path of travel;

a fusing unit located in fusing relation with a copy sheet moving alongsaid path of travel;

means mounting said fusing unit for movement along said path of travelin said one direction from an initial position to a final position andfor movement to a retracted safety position out of fusing relation witha copy sheet moving along said path of travel;

means to move said fusing unit from said initial position to said finalposition when a copy sheet is moving along said path of travel adjacentsaid fusing unit to extend the time the copy sheet is in fusing relationwith said fusing unit;

means to move said fusing unit to said retracted safety position out offusing relation with a copy sheet when a fault condition is detected;

said means to move said fusing unit from said initial position, to saidfinal position comprising a driven element;

means to couple said driven element with said fusing unit so that saiddriven element moves said fusing unit; and

said means to move said fusing unit to said retracted safety positioncomprising means to disengage said means to couple said driven elementwith said fusing unit.

7. Apparatus according to claim 6 further character- 15 ized by:

ized by:

means to re-engage said means to couple said driven element with saidfusing unit to move said fusing unit into fusing relation with a copysheet moving along said path of travel.

9. Apparatus for fusing an image on a copy sheet in a copying system orthe like comprising:

means to move a copy sheet in one direction along a path of travel;

a fusing unit located in fusing relation with a copy sheet moving alongsaid path of travel;

means mounting said fusing unit for movement along said path of travelin said one direction from an initial position to a final position andfor movement to a retracted safety position out of fusing relation witha copy sheet moving along said path of travel;

means to move said fusing unit from said initial position to said finalposition when a copy sheet is moving along said path of travel adjacentsaid fusing unit to extend the time the copy sheet is in fusing relationwith said fusing unit;

means to move said fusing unit to said retracted safety position out offusing relation with a copy sheet when a fault condition is detected;

said means to move said fusing unit from said initial position to saidfinal position comprising a cam;

cam follower means for coupling said cam with said fusing unit;

said cam follower means comprising a cam follower element and a linkagemeans;

said linkage means comprising a pair of levers;

one of said levers mounting said cam follower element;

a latch member normally latching said levers in rigid coupled relationwith respect to each other;

biasing means connected to said one of said levers for maintaining saidcam follower element in engagement with said cam; and

means to actuate said latch member to cause movement of said one of saidlevers relative to said other of said levers, said cam follower elementand said cam to move said fusing unit to said retracted safety position.10. Apparatus according to claim 9 further characterized means torelatch said latch member in response to movement of said cam to movesaid fusing unit from said retracted safety position to said initialposition. 11. Apparatus according to claim 10 further characterized by:

said means to relatch comprises a plurality of stationary stops and aresetting member; and

said resetting member being carried by one of said pair of levers.

12. Apparatus for fusing an image on a copy sheet in a copying system orthe like comprising:

means to move a copy sheet in one direction along a path of travel;

a fusing unit located in fusing relation with a copy sheet moving alongsaid path of travel;

means mounting said fusing unit for movement along said path of travelfrom a fusing position in fusing relation with a copy sheet moving alongsaid path of travel to a retracted safety position out of fusingrelation with a copy sheet moving along said path of travel;

means to move said fusing unit to said retracted safety position out offusing relation with a copy sheet when a fault condition is detected;

a fusing unit receiving assembly located at said retracted safetyposition; and

said fusing unit receiving assembly comprising a shield located betweensaid fusing unit and said path of travel when said fusing unit is insaid retracted safety position.

13. Apparatus for fusing an image on a copy sheet in a copying system orthe like comprising:

means to move a copy sheet in one direction along a path of travel;

a fusing unit located in fusing relation with a copy sheet moving alongsaid path of travel;

means mounting said fusing unit for movement along said path of travelfrom a fusing position in fusing relation with a copy sheet moving alongsaid path of travel to a retracted safety position out of fusingrelation with a copy sheet moving along said path of travel;

means to move said fusing unit to said retracted safety position out offusing relation with a copy sheet when a fault condition is detected;

a fusing unit receiving assembly mounted adjacent and to one side ofsaid fusing unit when said fusing unit is located in fusing relationwith a copy sheet moving along said path of travel;

said fusing unit receiving assembly being pocket-shaped with an openingfacing said fusing unit to permit the movement of said fusing unit intosaid assembly; and

said fusing unit receiving assembly comprising a shield located betweensaid fusing unit and said path of travel when said fusing unit islocated in said retracted position.

14. Apparatus according to claim 13 further characterized by:

means mounting said fusing unit for movement along said path of travelin said one direction from an initial position to a final position whilein fusing relation with a copy sheet moving along said path of travel;and

means to move said fusing unit from said initial position to said finalposition when a copy sheet is moving along said path of travel adjacentsaid fusing unit to extend the time the copy sheet is in fusing relationwith said fusing unit.

V 15. The method of fusing marking material to a copy 6 unit to extendthe time the copy sheet is in fusing relation with said fusing unit; and

moving said fusing unit along said path of travel to a retracted safetyposition disposed along said path of travel out of fusing relation witha copy sheet moving along said path of travel when a predeterminedcondition is detected.

16. Apparatus for fusing an image on a copy sheet in a copying system orthe like comprising:

means to move a copy sheet in one direction along a path of travel;

a fusing unit located in fusing relation with a copy sheet moving alongsaid path of travel;

means mounting said fusing unit for movement along said path of travelin said one direction from an initial position to a final position andfor movement along said path of travel to a retracted safety positiondisposed along said path of travel;

means to move said fusing unit along said path of travel in said onedirection from said initial position to said final position when a copysheet is moving along said path of travel adjacent said fusing unit toextend the time the copy sheet is in fusing relation with said fusingunit; and

means to move said fusing unit along said path of travel to saidretracted safety position.

17. Apparatus according to claim 16 further characterized by:

a fusing unit receiving assembly located at said retracted safetyposition; and said fusing unit receiving assembly comprising a shieldlocated between said fusing unit and said path of travel. 18. Apparatusaccording to claim 16 further characterized by:

- a fusing unit receiving assembly located at said retracted safetyposition and mounted adjacent said fusing unit when said fusing unit ispositioned in fusing relation with a copy sheet moving along said pathof travel; and

said fusing unit receiving assembly being pocket-shaped with an openingfacing said fusing unit to permit the movement of said fusing unit intosaid assembly.

19. Apparatus according to claim 16 further character- 45 ized by:

said means to move said fusing unit from said initial position to saidfinal position comprises a cam;

cam follower means drivingly interconnecting said cam and said fusingunit;

means to effect relative movement between said cam and said cam followermeans; and

said means to move said fusing unit along said path of travel to saidretracted safety position comprises means to disengage cam followermeans and said cam.

References Cited UNITED STATES PATENTS 3,053,962 9/1962 Cerasani et a1.219-388 3,197,614 7/1965 Engelstad et al 219388 3,219,326 11/1965 Hunt.

JOHN J. CAMBY, Primary Examiner US. Cl. X.R. l9. 88

